/*
Copyright 2015 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package controller

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"text/template"
	"time"

	"github.com/golang/glog"

	proxyproto "github.com/armon/go-proxyproto"
	"github.com/eapache/channels"
	apiv1 "k8s.io/api/core/v1"
	"k8s.io/client-go/kubernetes/scheme"
	v1core "k8s.io/client-go/kubernetes/typed/core/v1"
	"k8s.io/client-go/tools/record"
	"k8s.io/client-go/util/flowcontrol"
	"k8s.io/kubernetes/pkg/util/filesystem"

	"k8s.io/ingress-nginx/internal/file"
	"k8s.io/ingress-nginx/internal/ingress"
	"k8s.io/ingress-nginx/internal/ingress/annotations"
	"k8s.io/ingress-nginx/internal/ingress/annotations/class"
	ngx_config "k8s.io/ingress-nginx/internal/ingress/controller/config"
	"k8s.io/ingress-nginx/internal/ingress/controller/process"
	"k8s.io/ingress-nginx/internal/ingress/controller/store"
	ngx_template "k8s.io/ingress-nginx/internal/ingress/controller/template"
	"k8s.io/ingress-nginx/internal/ingress/status"
	ing_net "k8s.io/ingress-nginx/internal/net"
	"k8s.io/ingress-nginx/internal/net/dns"
	"k8s.io/ingress-nginx/internal/net/ssl"
	"k8s.io/ingress-nginx/internal/task"
	"k8s.io/ingress-nginx/internal/watch"
)

const (
	ngxHealthPath = "/healthz"
)

var (
	tmplPath = "/etc/nginx/template/nginx.tmpl"
)

// NewNGINXController creates a new NGINX Ingress controller.
func NewNGINXController(config *Configuration, fs file.Filesystem) *NGINXController {
	eventBroadcaster := record.NewBroadcaster()
	eventBroadcaster.StartLogging(glog.Infof)
	eventBroadcaster.StartRecordingToSink(&v1core.EventSinkImpl{
		Interface: config.Client.CoreV1().Events(config.Namespace),
	})

	h, err := dns.GetSystemNameServers()
	if err != nil {
		glog.Warningf("Error reading system nameservers: %v", err)
	}

	n := &NGINXController{
		isIPV6Enabled: ing_net.IsIPv6Enabled(),

		resolver:        h,
		cfg:             config,
		syncRateLimiter: flowcontrol.NewTokenBucketRateLimiter(config.SyncRateLimit, 1),

		recorder: eventBroadcaster.NewRecorder(scheme.Scheme, apiv1.EventSource{
			Component: "nginx-ingress-controller",
		}),

		stopCh:   make(chan struct{}),
		updateCh: channels.NewRingChannel(1024),

		stopLock: &sync.Mutex{},

		fileSystem: fs,

		runningConfig: new(ingress.Configuration),

		Proxy: &TCPProxy{},
	}

	n.store = store.New(
		config.EnableSSLChainCompletion,
		config.Namespace,
		config.ConfigMapName,
		config.TCPConfigMapName,
		config.UDPConfigMapName,
		config.DefaultSSLCertificate,
		config.ResyncPeriod,
		config.Client,
		fs,
		n.updateCh)

	n.syncQueue = task.NewTaskQueue(n.syncIngress)

	n.annotations = annotations.NewAnnotationExtractor(n.store)

	if config.UpdateStatus {
		n.syncStatus = status.NewStatusSyncer(status.Config{
			Client:                 config.Client,
			PublishService:         config.PublishService,
			PublishStatusAddress:   config.PublishStatusAddress,
			IngressLister:          n.store,
			ElectionID:             config.ElectionID,
			IngressClass:           class.IngressClass,
			DefaultIngressClass:    class.DefaultClass,
			UpdateStatusOnShutdown: config.UpdateStatusOnShutdown,
			UseNodeInternalIP:      config.UseNodeInternalIP,
		})
	} else {
		glog.Warning("Update of Ingress status is disabled (flag --update-status)")
	}

	onTemplateChange := func() {
		template, err := ngx_template.NewTemplate(tmplPath, fs)
		if err != nil {
			// this error is different from the rest because it must be clear why nginx is not working
			glog.Errorf(`
-------------------------------------------------------------------------------
Error loading new template: %v
-------------------------------------------------------------------------------
`, err)
			return
		}

		n.t = template
		glog.Info("New NGINX configuration template loaded.")
		n.syncQueue.EnqueueTask(task.GetDummyObject("template-change"))
	}

	ngxTpl, err := ngx_template.NewTemplate(tmplPath, fs)
	if err != nil {
		glog.Fatalf("Invalid NGINX configuration template: %v", err)
	}

	n.t = ngxTpl

	if _, ok := fs.(filesystem.DefaultFs); !ok {
		// do not setup watchers on tests
		return n
	}

	_, err = watch.NewFileWatcher(tmplPath, onTemplateChange)
	if err != nil {
		glog.Fatalf("Error creating file watcher for %v: %v", tmplPath, err)
	}

	filesToWatch := []string{}
	err = filepath.Walk("/etc/nginx/geoip/", func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if info.IsDir() {
			return nil
		}

		filesToWatch = append(filesToWatch, path)
		return nil
	})

	if err != nil {
		glog.Fatalf("Error creating file watchers: %v", err)
	}

	for _, f := range filesToWatch {
		_, err = watch.NewFileWatcher(f, func() {
			glog.Info("File %v changed. Reloading NGINX", f)
			n.syncQueue.EnqueueTask(task.GetDummyObject("file-change"))
		})
		if err != nil {
			glog.Fatalf("Error creating file watcher for %v: %v", f, err)
		}
	}

	return n
}

// NGINXController describes a NGINX Ingress controller.
type NGINXController struct {
	cfg *Configuration

	annotations annotations.Extractor

	recorder record.EventRecorder

	syncQueue *task.Queue

	syncStatus status.Sync

	syncRateLimiter flowcontrol.RateLimiter

	// stopLock is used to enforce that only a single call to Stop send at
	// a given time. We allow stopping through an HTTP endpoint and
	// allowing concurrent stoppers leads to stack traces.
	stopLock *sync.Mutex

	stopCh   chan struct{}
	updateCh *channels.RingChannel

	// ngxErrCh is used to detect errors with the NGINX processes
	ngxErrCh chan error

	// runningConfig contains the running configuration in the Backend
	runningConfig *ingress.Configuration

	t *ngx_template.Template

	resolver []net.IP

	isIPV6Enabled bool

	isShuttingDown bool

	Proxy *TCPProxy

	store store.Storer

	fileSystem filesystem.Filesystem
}

// Start starts a new NGINX master process running in the foreground.
func (n *NGINXController) Start() {
	glog.Infof("Starting NGINX Ingress controller")

	n.store.Run(n.stopCh)

	if n.syncStatus != nil {
		go n.syncStatus.Run()
	}

	cmd := nginxExecCommand()

	// put NGINX in another process group to prevent it
	// to receive signals meant for the controller
	cmd.SysProcAttr = &syscall.SysProcAttr{
		Setpgid: true,
		Pgid:    0,
	}

	if n.cfg.EnableSSLPassthrough {
		n.setupSSLProxy()
	}

	glog.Info("Starting NGINX process")
	n.start(cmd)

	go n.syncQueue.Run(time.Second, n.stopCh)
	// force initial sync
	n.syncQueue.EnqueueTask(task.GetDummyObject("initial-sync"))

	for {
		select {
		case err := <-n.ngxErrCh:
			if n.isShuttingDown {
				break
			}

			// if the nginx master process dies the workers continue to process requests,
			// passing checks but in case of updates in ingress no updates will be
			// reflected in the nginx configuration which can lead to confusion and report
			// issues because of this behavior.
			// To avoid this issue we restart nginx in case of errors.
			if process.IsRespawnIfRequired(err) {
				process.WaitUntilPortIsAvailable(n.cfg.ListenPorts.HTTP)
				// release command resources
				cmd.Process.Release()
				// start a new nginx master process if the controller is not being stopped
				cmd = nginxExecCommand()
				cmd.SysProcAttr = &syscall.SysProcAttr{
					Setpgid: true,
					Pgid:    0,
				}
				n.start(cmd)
			}
		case event := <-n.updateCh.Out():
			if n.isShuttingDown {
				break
			}
			if evt, ok := event.(store.Event); ok {
				glog.V(3).Infof("Event %v received - object %v", evt.Type, evt.Obj)
				if evt.Type == store.ConfigurationEvent {
					// TODO: is this necessary? Consider removing this special case
					n.syncQueue.EnqueueTask(task.GetDummyObject("configmap-change"))
					continue
				}

				n.syncQueue.EnqueueSkippableTask(evt.Obj)
			} else {
				glog.Warningf("Unexpected event type received %T", event)
			}
		case <-n.stopCh:
			break
		}
	}
}

// Stop gracefully stops the NGINX master process.
func (n *NGINXController) Stop() error {
	n.isShuttingDown = true

	n.stopLock.Lock()
	defer n.stopLock.Unlock()

	if n.syncQueue.IsShuttingDown() {
		return fmt.Errorf("shutdown already in progress")
	}

	glog.Infof("Shutting down controller queues")
	close(n.stopCh)
	go n.syncQueue.Shutdown()
	if n.syncStatus != nil {
		n.syncStatus.Shutdown()
	}

	// send stop signal to NGINX
	glog.Info("Stopping NGINX process")
	cmd := nginxExecCommand("-s", "quit")
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	err := cmd.Run()
	if err != nil {
		return err
	}

	// wait for the NGINX process to terminate
	timer := time.NewTicker(time.Second * 1)
	for range timer.C {
		if !process.IsNginxRunning() {
			glog.Info("NGINX process has stopped")
			timer.Stop()
			break
		}
	}

	return nil
}

func (n *NGINXController) start(cmd *exec.Cmd) {
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Start(); err != nil {
		glog.Fatalf("NGINX error: %v", err)
		n.ngxErrCh <- err
		return
	}

	go func() {
		n.ngxErrCh <- cmd.Wait()
	}()
}

// DefaultEndpoint returns the default endpoint to be use as default server that returns 404.
func (n NGINXController) DefaultEndpoint() ingress.Endpoint {
	return ingress.Endpoint{
		Address: "127.0.0.1",
		Port:    fmt.Sprintf("%v", n.cfg.ListenPorts.Default),
		Target:  &apiv1.ObjectReference{},
	}
}

// testTemplate checks if the NGINX configuration inside the byte array is valid
// running the command "nginx -t" using a temporal file.
func (n NGINXController) testTemplate(cfg []byte) error {
	if len(cfg) == 0 {
		return fmt.Errorf("Invalid NGINX configuration (empty)")
	}
	tmpfile, err := ioutil.TempFile("", "nginx-cfg")
	if err != nil {
		return err
	}
	defer tmpfile.Close()
	err = ioutil.WriteFile(tmpfile.Name(), cfg, file.ReadWriteByUser)
	if err != nil {
		return err
	}
	out, err := nginxTestCommand(tmpfile.Name()).CombinedOutput()
	if err != nil {
		// this error is different from the rest because it must be clear why nginx is not working
		oe := fmt.Sprintf(`
-------------------------------------------------------------------------------
Error: %v
%v
-------------------------------------------------------------------------------
`, err, string(out))
		return errors.New(oe)
	}

	os.Remove(tmpfile.Name())
	return nil
}

// OnUpdate is called by the synchronization loop whenever configuration
// changes were detected. The received backend Configuration is merged with the
// configuration ConfigMap before generating the final configuration file.
// Returns nil in case the backend was successfully reloaded.
func (n *NGINXController) OnUpdate(ingressCfg ingress.Configuration) error {
	cfg := n.store.GetBackendConfiguration()
	cfg.Resolver = n.resolver

	if n.cfg.EnableSSLPassthrough {
		servers := []*TCPServer{}
		for _, pb := range ingressCfg.PassthroughBackends {
			svc := pb.Service
			if svc == nil {
				glog.Warningf("Missing Service for SSL Passthrough backend %q", pb.Backend)
				continue
			}
			port, err := strconv.Atoi(pb.Port.String())
			if err != nil {
				for _, sp := range svc.Spec.Ports {
					if sp.Name == pb.Port.String() {
						port = int(sp.Port)
						break
					}
				}
			} else {
				for _, sp := range svc.Spec.Ports {
					if sp.Port == int32(port) {
						port = int(sp.Port)
						break
					}
				}
			}

			// TODO: Allow PassthroughBackends to specify they support proxy-protocol
			servers = append(servers, &TCPServer{
				Hostname:      pb.Hostname,
				IP:            svc.Spec.ClusterIP,
				Port:          port,
				ProxyProtocol: false,
			})
		}

		n.Proxy.ServerList = servers
	}

	// NGINX cannot resize the hash tables used to store server names. For
	// this reason we check if the current size is correct for the host
	// names defined in the Ingress rules and adjust the value if
	// necessary.
	// https://trac.nginx.org/nginx/ticket/352
	// https://trac.nginx.org/nginx/ticket/631
	var longestName int
	var serverNameBytes int
	redirectServers := make(map[string]string)
	for _, srv := range ingressCfg.Servers {
		if longestName < len(srv.Hostname) {
			longestName = len(srv.Hostname)
		}
		serverNameBytes += len(srv.Hostname)
		if srv.RedirectFromToWWW {
			var n string
			if strings.HasPrefix(srv.Hostname, "www.") {
				n = strings.TrimPrefix(srv.Hostname, "www.")
			} else {
				n = fmt.Sprintf("www.%v", srv.Hostname)
			}
			glog.V(3).Infof("Creating redirect from %q to %q", srv.Hostname, n)
			if _, ok := redirectServers[n]; !ok {
				found := false
				for _, esrv := range ingressCfg.Servers {
					if esrv.Hostname == n {
						found = true
						break
					}
				}
				if !found {
					redirectServers[n] = srv.Hostname
				}
			}
		}
	}
	if cfg.ServerNameHashBucketSize == 0 {
		nameHashBucketSize := nginxHashBucketSize(longestName)
		glog.V(3).Infof("Adjusting ServerNameHashBucketSize variable to %q", nameHashBucketSize)
		cfg.ServerNameHashBucketSize = nameHashBucketSize
	}
	serverNameHashMaxSize := nextPowerOf2(serverNameBytes)
	if cfg.ServerNameHashMaxSize < serverNameHashMaxSize {
		glog.V(3).Infof("Adjusting ServerNameHashMaxSize variable to %q", serverNameHashMaxSize)
		cfg.ServerNameHashMaxSize = serverNameHashMaxSize
	}

	// the limit of open files is per worker process
	// and we leave some room to avoid consuming all the FDs available
	wp, err := strconv.Atoi(cfg.WorkerProcesses)
	glog.V(3).Infof("Number of worker processes: %d", wp)
	if err != nil {
		wp = 1
	}
	maxOpenFiles := (sysctlFSFileMax() / wp) - 1024
	glog.V(2).Infof("Maximum number of open file descriptors: %d", maxOpenFiles)
	if maxOpenFiles < 1024 {
		// this means the value of RLIMIT_NOFILE is too low.
		maxOpenFiles = 1024
	}

	setHeaders := map[string]string{}
	if cfg.ProxySetHeaders != "" {
		cmap, err := n.store.GetConfigMap(cfg.ProxySetHeaders)
		if err != nil {
			glog.Warningf("Error reading ConfigMap %q from local store: %v", cfg.ProxySetHeaders, err)
		}

		setHeaders = cmap.Data
	}

	addHeaders := map[string]string{}
	if cfg.AddHeaders != "" {
		cmap, err := n.store.GetConfigMap(cfg.AddHeaders)
		if err != nil {
			glog.Warningf("Error reading ConfigMap %q from local store: %v", cfg.AddHeaders, err)
		}

		addHeaders = cmap.Data
	}

	sslDHParam := ""
	if cfg.SSLDHParam != "" {
		secretName := cfg.SSLDHParam

		secret, err := n.store.GetSecret(secretName)
		if err != nil {
			glog.Warningf("Error reading Secret %q from local store: %v", secretName, err)
		}

		nsSecName := strings.Replace(secretName, "/", "-", -1)

		dh, ok := secret.Data["dhparam.pem"]
		if ok {
			pemFileName, err := ssl.AddOrUpdateDHParam(nsSecName, dh, n.fileSystem)
			if err != nil {
				glog.Warningf("Error adding or updating dhparam file %v: %v", nsSecName, err)
			} else {
				sslDHParam = pemFileName
			}
		}
	}

	cfg.SSLDHParam = sslDHParam

	tc := ngx_config.TemplateConfig{
		ProxySetHeaders:             setHeaders,
		AddHeaders:                  addHeaders,
		MaxOpenFiles:                maxOpenFiles,
		BacklogSize:                 sysctlSomaxconn(),
		Backends:                    ingressCfg.Backends,
		PassthroughBackends:         ingressCfg.PassthroughBackends,
		Servers:                     ingressCfg.Servers,
		TCPBackends:                 ingressCfg.TCPEndpoints,
		UDPBackends:                 ingressCfg.UDPEndpoints,
		HealthzURI:                  ngxHealthPath,
		CustomErrors:                len(cfg.CustomHTTPErrors) > 0,
		Cfg:                         cfg,
		IsIPV6Enabled:               n.isIPV6Enabled && !cfg.DisableIpv6,
		NginxStatusIpv4Whitelist:    cfg.NginxStatusIpv4Whitelist,
		NginxStatusIpv6Whitelist:    cfg.NginxStatusIpv6Whitelist,
		RedirectServers:             redirectServers,
		IsSSLPassthroughEnabled:     n.cfg.EnableSSLPassthrough,
		ListenPorts:                 n.cfg.ListenPorts,
		PublishService:              n.GetPublishService(),
		DynamicConfigurationEnabled: n.cfg.DynamicConfigurationEnabled,
		DisableLua:                  n.cfg.DisableLua,
	}

	content, err := n.t.Write(tc)
	if err != nil {
		return err
	}

	if cfg.EnableOpentracing {
		err := createOpentracingCfg(cfg)
		if err != nil {
			return err
		}
	}

	err = n.testTemplate(content)
	if err != nil {
		return err
	}

	if glog.V(2) {
		src, _ := ioutil.ReadFile(cfgPath)
		if !bytes.Equal(src, content) {
			tmpfile, err := ioutil.TempFile("", "new-nginx-cfg")
			if err != nil {
				return err
			}
			defer tmpfile.Close()
			err = ioutil.WriteFile(tmpfile.Name(), content, file.ReadWriteByUser)
			if err != nil {
				return err
			}

			// TODO: executing diff can return exit code != 0
			diffOutput, _ := exec.Command("diff", "-u", cfgPath, tmpfile.Name()).CombinedOutput()

			glog.Infof("NGINX configuration diff:\n%v", string(diffOutput))

			// we do not defer the deletion of temp files in order
			// to keep them around for inspection in case of error
			os.Remove(tmpfile.Name())
		}
	}

	err = ioutil.WriteFile(cfgPath, content, file.ReadWriteByUser)
	if err != nil {
		return err
	}

	o, err := nginxExecCommand("-s", "reload").CombinedOutput()
	if err != nil {
		return fmt.Errorf("%v\n%v", err, string(o))
	}

	return nil
}

// nginxHashBucketSize computes the correct NGINX hash_bucket_size for a hash
// with the given longest key.
func nginxHashBucketSize(longestString int) int {
	// see https://github.com/kubernetes/ingress-nginxs/issues/623 for an explanation
	wordSize := 8 // Assume 64 bit CPU
	n := longestString + 2
	aligned := (n + wordSize - 1) & ^(wordSize - 1)
	rawSize := wordSize + wordSize + aligned
	return nextPowerOf2(rawSize)
}

// http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
// https://play.golang.org/p/TVSyCcdxUh
func nextPowerOf2(v int) int {
	v--
	v |= v >> 1
	v |= v >> 2
	v |= v >> 4
	v |= v >> 8
	v |= v >> 16
	v++

	return v
}

func (n *NGINXController) setupSSLProxy() {
	cfg := n.store.GetBackendConfiguration()
	sslPort := n.cfg.ListenPorts.HTTPS
	proxyPort := n.cfg.ListenPorts.SSLProxy

	glog.Info("Starting TLS proxy for SSL Passthrough")
	n.Proxy = &TCPProxy{
		Default: &TCPServer{
			Hostname:      "localhost",
			IP:            "127.0.0.1",
			Port:          proxyPort,
			ProxyProtocol: true,
		},
	}

	listener, err := net.Listen("tcp", fmt.Sprintf(":%v", sslPort))
	if err != nil {
		glog.Fatalf("%v", err)
	}

	proxyList := &proxyproto.Listener{Listener: listener, ProxyHeaderTimeout: cfg.ProxyProtocolHeaderTimeout}

	// accept TCP connections on the configured HTTPS port
	go func() {
		for {
			var conn net.Conn
			var err error

			if n.store.GetBackendConfiguration().UseProxyProtocol {
				// wrap the listener in order to decode Proxy
				// Protocol before handling the connection
				conn, err = proxyList.Accept()
			} else {
				conn, err = listener.Accept()
			}

			if err != nil {
				glog.Warningf("Error accepting TCP connection: %v", err)
				continue
			}

			glog.V(3).Infof("Handling connection from remote address %s to local %s", conn.RemoteAddr(), conn.LocalAddr())
			go n.Proxy.Handle(conn)
		}
	}()
}

// IsDynamicConfigurationEnough returns whether a Configuration can be
// dynamically applied, without reloading the backend.
func (n *NGINXController) IsDynamicConfigurationEnough(pcfg *ingress.Configuration) bool {
	copyOfRunningConfig := *n.runningConfig
	copyOfPcfg := *pcfg

	copyOfRunningConfig.Backends = []*ingress.Backend{}
	copyOfPcfg.Backends = []*ingress.Backend{}

	return copyOfRunningConfig.Equal(&copyOfPcfg)
}

// configureDynamically encodes new Backends in JSON format and POSTs the
// payload to an internal HTTP endpoint handled by Lua.
func configureDynamically(pcfg *ingress.Configuration, port int) error {
	backends := make([]*ingress.Backend, len(pcfg.Backends))

	for i, backend := range pcfg.Backends {
		luaBackend := &ingress.Backend{
			Name:            backend.Name,
			Port:            backend.Port,
			Secure:          backend.Secure,
			SSLPassthrough:  backend.SSLPassthrough,
			SessionAffinity: backend.SessionAffinity,
			UpstreamHashBy:  backend.UpstreamHashBy,
			LoadBalancing:   backend.LoadBalancing,
		}

		var endpoints []ingress.Endpoint
		for _, endpoint := range backend.Endpoints {
			endpoints = append(endpoints, ingress.Endpoint{
				Address:     endpoint.Address,
				FailTimeout: endpoint.FailTimeout,
				MaxFails:    endpoint.MaxFails,
				Port:        endpoint.Port,
			})
		}

		luaBackend.Endpoints = endpoints
		backends[i] = luaBackend
	}

	buf, err := json.Marshal(backends)
	if err != nil {
		return err
	}

	glog.V(2).Infof("Posting backends configuration: %s", buf)

	url := fmt.Sprintf("http://localhost:%d/configuration/backends", port)
	resp, err := http.Post(url, "application/json", bytes.NewReader(buf))
	if err != nil {
		return err
	}

	defer func() {
		if err := resp.Body.Close(); err != nil {
			glog.Warningf("Error while closing response body:\n%v", err)
		}
	}()

	if resp.StatusCode != http.StatusCreated {
		return fmt.Errorf("Unexpected error code: %d", resp.StatusCode)
	}

	return nil
}

const zipkinTmpl = `{
  "service_name": "{{ .ZipkinServiceName }}",
  "collector_host": "{{ .ZipkinCollectorHost }}",
  "collector_port": {{ .ZipkinCollectorPort }},
  "sample_rate": {{ .ZipkinSampleRate }}
}`

const jaegerTmpl = `{
  "service_name": "{{ .JaegerServiceName }}",
  "sampler": {
	"type": "{{ .JaegerSamplerType }}",
	"param": {{ .JaegerSamplerParam }}
  },
  "reporter": {
	"localAgentHostPort": "{{ .JaegerCollectorHost }}:{{ .JaegerCollectorPort }}"
  }
}`

func createOpentracingCfg(cfg ngx_config.Configuration) error {
	var tmpl *template.Template
	var err error

	if cfg.ZipkinCollectorHost != "" {
		tmpl, err = template.New("zipkin").Parse(zipkinTmpl)
		if err != nil {
			return err
		}
	} else if cfg.JaegerCollectorHost != "" {
		tmpl, err = template.New("jarger").Parse(jaegerTmpl)
		if err != nil {
			return err
		}
	} else {
		tmpl, _ = template.New("empty").Parse("{}")
	}

	tmplBuf := bytes.NewBuffer(make([]byte, 0))
	err = tmpl.Execute(tmplBuf, cfg)
	if err != nil {
		return err
	}

	return ioutil.WriteFile("/etc/nginx/opentracing.json", tmplBuf.Bytes(), file.ReadWriteByUser)
}
